Safety lock switch



1968 R. J. PERSIA ETAL 3,370,498

SAFETY LOCK SWITCH Original Filed Sept. 19, 1963 2 Sheets-Sheet 1 INVENTORp'.

Feb. 27, 1968 R. J. PERSIA ETAL 3,370,498

SAFETY LOCK SWITCH Original Filed Sept. 19, 1963 2 Sheets-Sheet INVENTORS 4 United States Patent O 3,370,498 SAFETY LOCK SWITCH Raymond J. Persia, Farmington, John E. Arnold, Garden City, and Herbert A. Martens, Birmingham, Mich, assignors to Macliworth G. Rees, a division of Avis industrial Corporation, Detroit, Mich, a corporation of Delaware Original application Sept. 19, 1963, Ser. No. 310,081, now Patent No. 3,321.589, dated May 23, 1967. Divided and this application Nov. 7, 1966, Ser. No. 620,569

Claims. (Cl. 83-701) This application is a division of Ser. No. 310,081 filed Sept. 19, 1963.

This invention relates to safety lock switches and, more especially, to a switch of this type adapted particularly for use with punch presses and the like.

The switch of this invention has three positions to which the switch may be turned by a special key. With this key, the switch may be turned to On position for normal operation of the press and to Off and Lock positions in which the circuit to the press operating mechanism is open.

One of the objects is to provide a safety lock switch of the class described in which the key can be removed from the lock only in the Off position of the switch. With such a construction, the invention contemplates attaching the key, to a chain or other flexible element, to the safety block usually provided in presses to be placed between the dies to limit closing movement thereof. In accordance with the present invention, it is proposed to make the chain so short that the key must be removed from the lock in order to position the safety block between the dies of the press. Therefore, when the safety block is between the dies of the press, the key is of necessity removed from the lock, and the switch is in Off position. This assures anyone performing mechanical work on the press that the switch will not be inadvertently turned to On position.

Another object of the invention is to provide a switch of this type in which the switch may be secured to Lock position to prevent unauthorized operation of the press. When, for instance, the electrical circuits of the press are bein serviced, it may not be feasible to place the safety block between the dies of the press, and thus remove the key from the lock, because the ram may be in its lowered position or stalled in some other position where the safety block could not be used. In such an event, the serviceman moves the key to Lock position wherein it may be fastened by a padlock to a bracket on the switch. In this position of the switch, the circuit to the press operating mechanism is open so that the press cannot be operated and the key is locked in this position to prevent unauthorized or accidental closing of the switch.

Another object of the invention is to provide safety means in the lock whereby the lock can be actuated only by purposeful intent and not by accident. To this end, the spring pressed connecting link or disk which is actuated by the key is provided with a slot or recess which is engaged by a locking pin on the housing so that the key can rotate the connecting link only after the connecting link has been pressed inwardly by the key against the action of said spring to disengage the locking pin from the slot or recess in the connecting link. This safety feature is considered to be of considerable importance.

Another feature of this invention resides in the ruggedness of the key and lock. The key is attached to the safety block which may weigh in the neighborhood of 20 pounds and which is normally stored on a rack on or beside the press. In accordance with this invention, the key and lock are rugged enough to hold the weight of the safety block in the event it is dropped or knocked off its supporting rack, which sometimes happens. In accordance with this invention, the key and lock are constructed to stand up under this type of treatment.

Another important feature of the invention resides in the means provided for holding the key in On position. This consists of a slot or recess in the cap which receives the back edge of the bit or web of the key when the switch is in On position. When the key is in this position, it is urged into locking engagement with the slot or recess by the spring pressed connecting link. The bit or web of the key is disengaged from this slot or recess during the initial inward pressure on the key after the key is inserted. When the key is in this locked position, it cannot be turned inadvertently to interfere with the operation of the press when the latter is running. Such interference could occur by somebody or something moving past the press and brushing against the key so as to turn it. Also, the safety block could fall off its supporting rack and the weight of the falling block could turn the key and interrupt the operation of the press.

The various objects and advantages, and the novel details of construction of a commercially practical embodiment of the invention, will become more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, in which:

FIGURE 1 is a vertical sectional elevational view through a safety lock switch constructed in accordance with this invention, with the key shown fully inserted;

FIGURE 2 is a sectional elevational view of the lock portion shown in FIGURE 1 with the key partially inserted;

FIGURE 3 is a sectional view taken substantially on the plane indicated by line 33 in FIGURE 1;

FIGURE 4 is a similar view with the lock switch in Off position;

FIGURE 5 is a sectional view taken substantially on the plane indicated by line 55 in FIGURE 1;

FIGURE 6 is a broken away perspective view of the lock showing certain parts thereof;

FIGURE 7 is a perspective View of the lock switch; and

FIGURE 8 is a semidiametric view showing a press and the environment in which the invention is used.

The safety lock switch of this invention, as shown in FIGURES 1, 6 and 7, comprises a locking mechanism L, a switch mechanism S and a key K.

One environment in which the invention of this application may be used to advantage is shown diagrammatically in FIGURE 8. In this figure, there is illustrated a punch press or the like 10 having relatively movable dies 11 one of which is adapted to be reciprocated by means of a piston and cylinder or like mechanism 12. Presses of this general type are usually provided with sa safety block 13 adapted to be placed between the dies to prevent the closiug thereof during inoperative periods of the press. The safety block is usually lodged on a supporting rack or the like 14 secured to or arranged adjacent the press 10. The safety block 13 is attached to the key K by means of a chain or other flexible element 15. In accordance with this invention, it is proposed to make the chain 15 so short that the key K must be removed from the lock in order to position the safety block between the dies of the press. This assures anyone performing mechanical work on the press that the switch will not be inadvertently turned to On position.

The device comprises a cover 20 to the rear side of which the switch mechanism S is attached. The switch mechanism is of conventional construction and will only be briefly referred to. It consists of a movable contact arm 21 provided with roller contacts 22 at the opposite ends thereof. When the contacts 22 are in engagement with the contact terminals 23, the switch is in n posi- 3 tion. When the contact rollers 22 are located between the spaced contacts 24, the switch is Off position, and when the contact rollers22 engage the contact members 25, the switch is in Look position. The circuit to the operating mechanism of the press is closed when the contact arm 21 is swung to the position opposite to that shown in FIGURE wherein the contact rollers 22 engage the contacts 23. In the two other positions; that is, the Off position and the Lock position, the circuit to the press operating mechanism is open.

As stated, the switch mechanism is of conventional construction and hence my be varied as found necessary or expedient.

The movable contact arm 21 is actuated by a rotatable yoke member 30 rotatably mounted in a sleeve guide 31 secured within thecover 20. The yoke member 30 is providetl with a portion 32 engaging the contact arm 21 to actuate the same. The opposite end of the yoke member 3%) is provided with a tongue 33 adapted to enter a recess 34 to nonrotatably but sl-id'ably connect the yoke member :30 to a connecting link 01' disk 35 slidably mounted in a housing member 36 secured, as, for instance, by fasteners 37a to the cover 'I'hehou'sing 'member 36 is provided with an annular tflan'ge -37 at the forward or front face thereof which flange is piehded with a pair of opposed keyhole slots 38. The 63? K is provided with a handle portion 40, a stem portion 41, and a head, or hit, or web 42. In inserting the key K into the lock, the ends of the head or web 42 enter the keyhole slots 38 when the key is in a vertical position, such as shown in FIGURE 6, which is the Off position of the switch.

The link or disk member 35 is slidably mounted in a here 43 formed in the housing 36 and is urged towards the left and towards the annular flange 37 by means of a spring 44 which bears on the one hand against the confleeting link or disk 35 and on the other hand against the sleeve guide Thus, the connecting link ordisk 35 is normally iirged to the left, as viewed in FIGURES 1 and 2 normally feposes in the position illustrated in FIG- URE 2 in which it engages the annular flange 37. The connecting link or disk 35 is moved to the right, as viewed in these figures, when the key is inserted and pressed inwaidly against the forward flat face 45 of the disk or connecting 35-. This is the position of the parts illuseaten in FIGURE 1. When the head 42 of the key clears the keyhole slots 38, it is within the annular flange 37 and engages the face 45 of the connecting link 35 to move the same axially of the 7 housing 36 to compress the spring 44.

Means is provided so that the lock can be actuated only by purposeful intent, and to this end, the annular flange 37 is provided with one or more, here shown as two, locking pins 50 projecting inwardly from the annuar flange 37 and engaging recesses 51 formed in a flange 52 formed in the disk member 35. Thus, the disk member 35 must be forcefully moved to the right against the action of the spring 44 by the head 42 of the key K before the disk member 35 can be rotated. This prevents the lock from being accidentally operated by any unintended pressure on the key K. It will be obvious that when the connecting link or disk 35 is rotated by the key, the connection 33-34 with the yoke permits the yoke 30 to be rotated and the contact arm 21 to be actuated.

In order that the key K may engage the connecting link or disk to rotate the same, the flange 52 of the connecting link or disk 35 is provided with a pair of opposed slots '60 adapted to be engaged by the head 42 of the key when the same is inserted in the keyhole slots 38.

Thus, when the 'key is inserted into the lock through the keyhole slots 38, it will engage the opposed slots or recesses 60 in the flange 52 of the connecting link 35 and upon continued inward pressure of the key, the connecting link 35 will be pressed inwardly against the action of the spring 44 to move the slots 51 clear of the locking pins 4 50. Thereupon, by turning the key, the connecting link may be rotated and through the connection 33-34 Wlll rotate the yoke member 30 and actuate the contact arm 21.

In order to lock the key in On position, the annular flange 37 on the housing 36 is provided with a pair of opposed recesses 70 in which the back edges of the head 42 on the key may engage in the On position of the lock. The head 42 of the key is held in engagement with the recesses 70 by the connecting link or disk 35 pressing thereagainst, which connecting link 35 is urged to the left by the spring 44. Thus, when the key is locked in this On position, it cannot be turned inadvertently t0 Off or Lock positions to interfere with the operationof the press when the latter is running. Such interference could occur by somebody or something moving past the press and brushing against the key so as to turn it. Also, the safety block 13 could fall off its supporting rack and the weight of the falling block could turn the key and interrupt the operation of the press. As stated, this is prevented by the engagement of the head 42 with the recesses 70 in the flange 37 of the housing 36.

The handle 40 of the key K is shown as provided with an opening 40a with which the end of the flexible arm or chain 15 is connected which connects the key to the safety block 13.

Another feature of the present invention resides in the means for positively securing the lock in the Lock position to prevent unauthorized operation of the press as, for instance, when the electrical circuits of the press are being serviced. Under suchcircumstances, it may not be feasible to place the safety block between the dies of the press and thus remove the key from the lock, because the ram of the press may be in its lowered position or the dies may be stalled in some intermediate position where the safey block 13 could not be used. Under such circumstances, the operator moves the key to Lock position wherein an aperture 40b in the handle 40 of the key K is brought adjacent a bracket 71 attached as at 72 to the cover 20. The bracket 71 is provided with an aperture 71a adapted to register with the aperture 40b whereupon a padlock 73 maybe employed to lock the key to the bracket to,

prevent the unauthorized or accidental operation of the lock and switch.

It should be pointed out that, as shown in the drawings, the key and lock are rugged enough to support the weight of the safety block 13 in the event it is dropped or knocked off its supporting rack, which sometimes happens. Moreover, such a catastrophe would not interfere with the lock and, hence, the switch in the On or Lock positions of the lock switch.

From the foregoing description, it will be apparent that when the key is first inserted into the lock, the head 42 passes through the keyhole slots 38, whereupon the head of the key is inside the annular flange 37 of the housing 36. The key head first engages the face 45 and the slots 60 of the connecting link or disk and upon continued pressure on the key, the connecting link 35 is moved to 'the right from the position illustrated in FIGURE 2 to that illustrated in FIGURE 1. This moves the recesses 51 from engagement with the lock pins 50 so that the connecting link 35 may 'be rotated to rotate the yoke member 30 and actuate the contact arm 21. When the lock is in On position and the key is released, the rear faces of the ends of the head 42 engage in the recesses 70 in the flange 37 to lock the switch in its On position. As also described, when the switch is moved to the Lock position, the key may be padlocked in this position to the bracket 71.

Also as described, the safety block 13 may be placed between the dies of the press only when the key K is removed from the lock and this can occur only when the lock switch is in Off position. Thus, it will be seen that there is provided a simple, rugged lock switch particularly adapted for use with punch pressures and the like and providing all of the safety factors desirable in an installation of this type.

While one commercially practical embodiment of the invention has been described and illustrated herein somewhat in detail, it will be understood that various changes may be made as may come within the purview of the accompanying claims.

What is claimed is:

1. In a press having movable parts, and a safety block adapted to be placed between said movable parts to prevent accidental closing of the dies of the press, that improvement which comprises, a lock switch adapted to control the circuit to the press operating mechanism, a key for actuating said switch, and means connecting said key to said safety block, said key and lock switch being rugged enough to support said safety block in the event it is dropped from its supporting rack.

2. In a press having movable parts, and a safety block adapted to be placed between said movable parts to prevent accidental closing of the dies of the press, that improvement which comprises, a switch adapted to control the circuit to the press operating mechanism, a key for actuating said switch removable therefrom only in the 01f position of the switch, and means connecting said key to the safety block of such a length whereby said key must be removed from said switch in order to position the safety block between the dies of the press.

3. The invention of claim 2 wherein said connecting means includes a flexible element connecting said key to the safety block and wherein the flexible element is of a length less than the distance between said switch and the dies of the press.

4. A device as described in claim 2 in which said switch and key are of sufiicient strength to support said safety block in the event it is dropped or knocked off its supporting rack.

5. The combination for use with a machine assembly having a plurality of relatively movable parts, a safct block adapted to be placed between the relatively movable parts for limiting the movement thereof, a lock switch assembly fixed to the machine assembly for controlling the energization of the machine including a lock switch and a key removable in an Off position of said switch assembly, and flexible means connecting said safety block and said removable key, said flexible means being of such length that said key must be removed from said lock switch assembly in order to position said safety block between the relatively movable parts, said lock switch having a pair of contacts controlled by the movement of said removable key in a plurality of positions, means for transmitting certain motions of said key to at least one of said contacts, housing means including means rigidly fastened to the machine, said housing means having inwardly extending flange means and at least one keyhole slot formed in said flange mans, said key having a head portion adapted to be inserted into said keyhole slot and subsequently positioned behind said flange means interior of said housing means for preventing the extraction of said key from said switch assembly and placing said safety block between the movable parts.

6. The combination of claim 5 wherein one of said contacts is movable and said means for transmitting includes a resiliently biased connecting link.

7. The combination of claim 6 wherein said flange means and said key head are of sufiicient mechanical strength to support the dropped Weight of said safety block.

8. The combination of claim 6 wherein the insertion of said head portion into said keyhole slot engages said connecting link to resiliently urge said connecting link inwardly, the inward motion of said connecting link forming an annular chamber between said connecting link and said flange for positioning said head behind said flange.

9. The combination of claim 8 wherein said flange means further includes means for locking said key head in said On position.

10. The combination of claim 9 wherein said flange means and said key head are of sufiicient mechanical strength to support the dropped weight of said safety block.

References Cited UNITED STATES PATENTS 4/1941 MacBlane 192l34 3/1943 Booth 192-134 ROBERT K. SCHAEFER, Primary Examiner. H. HOHAUSER, Assistant Examiner. 

1. IN A PRESS HAVING MOVABLE PARTS, AND A SAFETY BLOCK ADAPTED TO BE PLACED BETWEEN SAID MOVABLE PARTS TO PREVENT ACCIDENTAL CLOSING OF THE DIES OF THE PRESS, THAT IMPROVEMENT WHICH COMPRISES, A LOCK SWITCH ADAPTED TO CONTROL THE CIRCUIT TO THE PRESS OPERATING MECHANISM, A KEY FOR ACTUATING SAID SWITCH, AND MEANS CONNECTING SAID KEY TO SAID SAFETY BLOCK, SAID KEY AND LOCK SWITCH BEING RUGGED ENOUGH TO SUPPORT SAID SAFETY BLOCK IN THE EVENT IT IS DROPPED FROM ITS SUPPORTING RACK. 